Ogof Draenen industrial contamination

Andy Sparrow

Active member
While in the Draenen main streamway yesterday I was looking at the sediment deposits that completely cover the walls of the passage as far up as you can see.  I have not seen a deposit like this in any other cave.  It consists of typical brown mud covered with a thin blue-grey crust.  The entire length of the streamway is overlain by coal tips and it would seem likely that the blue-grey crust originates from this.  What seems inexplicable is the uniformity of the deposit rather than being confined to specific areas of surface leak-through.  It is almost as if the entire streamway went through a period of being filled with static water.  Could it be that there was an event that caused this?  This could have been a major collapse of the passage (Riflemans?), a dramatic increase of the sediment burden due to industrial processes, or the modification of the hydrology by mining activities.  Does anyone else have a view on this?
 

Peter Burgess

New member
Andy Sparrow said:
While in the Draenen main streamway yesterday I was looking at the sediment deposits that completely cover the walls of the passage as far up as you can see.  I have not seen a deposit like this in any other cave.  It consists of typical brown mud covered with a thin blue-grey crust.  The entire length of the streamway is overlain by coal tips and it would seem likely that the blue-grey crust originates from this.  What seems inexplicable is the uniformity of the deposit rather than being confined to specific areas of surface leak-through.  It is almost as if the entire streamway went through a period of being filled with static water.  Could it be that there was an event that caused this?  This could have been a major collapse of the passage (Riflemans?), a dramatic increase of the sediment burden due to industrial processes, or the modification of the hydrology by mining activities.  Does anyone else have a view on this?

Get it analysed, and then we might have something to go on.
 

Peter Burgess

New member
But while we can speculate without evidence, I woudl have expected the water leaching out of coal tips to contain ochre, like the bright yellow gunge that comes out of mine levels?
 

Andy Sparrow

Active member
Analysis would be interesting.  You could also probably pin a date down on the flood event by stal dating - there are very obvious post-event stal deposits that are pure white.  The most notable example is a muddied curtain with a centimetre or so of pure white along its lower edge. 
 

Rhian

New member
There are examples in Draenen where coal is seen interbedded with coarse sandy, cross laminated bedding. Ive always thought that they could represent periods of heavy rain washing coal seds into the cave but they could equally equate to times where catchment on the surface has changed because of the intense industrial activity on the surface.

I wonder if the uniformity is to do with the coal being so light and much of it gets carried along on the top of the water. As the water level falls it would coat the walls. As a child we used to swim in the Rhymney (Dont tell my Mum she'd kill me!). We used to come out covered in fine black glitter!

I hadn?t associated these with your observations that you made in the streamway but Im no expert. I know what you mean though. Interesting stuff
 

Les W

Active member
Andy Sparrow said:
Analysis would be interesting.  You could also probably pin a date down on the flood event by stal dating - there are very obvious post-event stal deposits that are pure white.  The most notable example is a muddied curtain with a centimetre or so of pure white along its lower edge. 
You could defiantly pin down a date by carbon dating the organic material in the mud itself.
 

Elaine

Active member
Surely that would just tell you how old the plant material was that went into forming the coal many moons ago. I suppose you could then compare it to the dated ages of any local coal seams to see where it originated. But it wouldn't tell you when it got into the cave.


Would it?
 

graham

New member
Elaine is (mostly) right and Les is wrong. a radiocarbon date on this would tell you nothing about when this deposit was laid down unless it was derived from living material. Radiocarbon dating measures the time that has passed since the carbonaceous material in question ceased to be part of living matter and thus the ratio of C12 to C14 isotopes ceases, through beta decay of the C14, to be the same as that of the atmosphere.

Elaine is wrong, however, in assuming that a radiocarbon determination can give a date for the coal seams from which it is assumed to be derived. The technique can only work on material up to 80,000 years old - way too young for any coal seam.

The guiding principle in all dating work is to carefully define exactly what the event is that you are measuring.
 

graham

New member
Andy's suggestion of dating post-flood stal wouldn't work, either. Again, what event are you dating? That active white stal will vary in age from immediately post-flood to yesterday.
 

Chris Lank

New member
Here are a couple of photographs from yesterday showing the deposits in the main streamway.  One shows the "mud" and the other one shows the "crust".

2449115921_9306b1ddaf.jpg


2449942514_72453e6e15.jpg
 

Les W

Active member
graham said:
Elaine is (mostly) right and Les is wrong.

I didn't mean date the coal.  :coffee:
Any flood deposits will contain organic material contemporaneous with that flood event. Separating out the relevant bits of the sediment to date might be a tad more difficult, but I'm sure science will give the answers.  :bow:
 

graham

New member
Les W said:
graham said:
Elaine is (mostly) right and Les is wrong.

I didn't mean date the coal.  :coffee:
Any flood deposits will contain organic material contemporaneous with that flood event. Separating out the relevant bits of the sediment to date might be a tad more difficult, but I'm sure science will give the answers.  :bow:

I know you didn't.  ::)

But you still need to understand the event that you are dating, which would not be the point at which some organic material became incorporated into the sediment. This is exactly the reason why I think it impossible to radiocarbon date the patina on open-air rock art panels, as some would claim.
 

Andy Sparrow

Active member
graham said:
Andy's suggestion of dating post-flood stal wouldn't work, either. Again, what event are you dating? That active white stal will vary in age from immediately post-flood to yesterday.

Don't you just take sample from the interface of the brown/white stal?
 

Rhian

New member
Are you sure thats coal? Could that be manganese?
I have found a nice paper talking about deopsits like this. It describes coatings of a mineral called birnessite on cave pebbles and forming "soot like layers on walls and other cave surfaces". Birnessite is a mineral oxide of manganese. http://www.minsocam.org/ammin/am64/am64_1219.pdf
Perhaps there are other theories...
 

Duncan Price

Active member
Rhian said:
Are you sure thats coal? Could that be manganese?
I have found a nice paper talking about deopsits like this. It describes coatings of a mineral called birnessite on cave pebbles and forming "soot like layers on walls and other cave surfaces". Birnessite is a mineral oxide of manganese. http://www.minsocam.org/ammin/am64/am64_1219.pdf
Perhaps there are other theories...

Rhian is along the right track.  Its is probably goethite (hydrated iron oxide) - the same stuff is deposited in Agen Allwedd in the turkey streamway and particularly in the Rememberance Series.
 

Rhian

New member
I know, I know, I need to get a life but these deposits have kindled an interested. I have done a bit of digging about Birnessite and Duncans Geothite and I thought that people might be interested in what Ive found.

Back in 1982 (Vol9 No3 Cave Science), Bill Gascoine wrote a paper on the black deposits in Welsh Caves.  This is mainly based on Mynydd Llangynidr and Llangattwg but includes Shambre Ddu. He points out that in his study area, at the interface of the Dowlais Limestone and the Millstone Grit, there is a thin band of iron and manganese rich shale.  In places it is rich in limonite, siderite, haematite and Wad. 

He didnt find evidence of the shale band at Pwll Du but does comment on deposits in Shambre Ddu to indicate its presence. These include black stal? and flowstone, some with yellow or orange crusts as well as black sediment coating the floor and some of the boulders and black flows. The black deposits in this cave contain high concentrations of manganese and aluminium as well as iron.

He concludes that ?the black deposits in the caves studied are formed by precipitation of iron(III) hydroxide and manganese(IV) oxide (on or in clays and sands). These originate from a shale band  above the Dowlais limestone and are carried to the lower levels dissolved in water. Their occurrence at or near points where water enters the cave is due to oxidation by air encouraging precipitation at that point.?

Im no expert Im just re-telling Bills story but I am getting more and more convinced that your coal is actually mineral? manganese or iron, I don?t know but if someone wants to know the answer, his very detailed paper tells you exactly how, if you have a mate with a lab!
 
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